The present invention relates to a separation type detector which is used in a separation type extinction optical smoke detector in a fire alarm system or a burglar alarm system utilizing an ultrasonic wave, and which includes a transmission unit such as a light source or a sound wave source, and a reception unit separated from the transmission unit.
Conventional extinction smoke detectors in fire alarm systems include a separation type detector. The separation type detector has light-emitting and light-receiving units separated from each other by a distance of 10 m or more. Japanese Utility Model Diclosure No. 57-124758, incorporated herein, describes a "Separation Type Extinction Smoke Detector". Other conventional fire alarm systems have also been proposed. For example, in one system, a transmission circuit is arranged in each fire detector, and a receiver discriminates which detector is operated. In another system, a detected analog signal is sent back to a receiver. A typical example is described in Japanese Patent Disclosure No. 59-91597, incorporated herein, entitled an "Abnormality Alarm System".
In order to improve a S/N (signal-to-noise) ratio and save power in a conventional separation type extinction optical smoke detector, light beams are emitted as pulse beams to synchronize the light-emitting unit with the light-receiving unit. For this reason, a sync signal line is required between the light-emitting and light-receiving units. Since the length of the signal line is several tens of meters, electrical noise reduction must be taken into consideration.